A huge amount of video content is now viewed on home computers and there is an increasing desire to view content downloaded, streamed and stored on home computers on televisions throughout a user's property. Typically this has involved connecting the computer directly to the television via a video output such as VGA, composite or HDMI.
The advent of wireless network technology has allowed video streaming to be provided without a hard-wired connection to the computer. More recently transmission standards such as Wireless USB have enabled provided high performance transmission of bandwidth heavy content, such as high definition video footage to be streamed wirelessly between devices. A USB dongle is connected to the computer to transmit the video data, and a receiver, such as a network streaming device wirelessly receives the content. Such network streaming devices, connected to a television or more recently integrated into a television have therefore allowed content stored on a home computer to be made available for display on a television.
One standard for enabling interactivity between devices has been provided by the Digital Living Network Alliance (DNLA) to allow electronic devices to send and receive multimedia content. The DLNA standard defines a subset of the UPnP standard for interoperability between home entertainment devices. The network streaming device reads the video file from the computer and renders the video from the file for viewing on the connected television. Such access could be over Wireless USB for example.
However, video transmission issues exist, in particular for screencasting. Screencasting is a process whereby all, or a portion of a computer desktop display is replicated to another display such as a television. Preferably audio is also captured and multiplexed with the video. In this arrangement, there is no file or item of video content for the network streaming device to access and thus alternative solutions are required.
One approach for screencasting is to read memory dedicated to a graphics card to capture bitmaps of the displayed data. There are however many challenges faced with this approach, including capturing uncompressed video data, retransmitting such data, minimising delay between the computer and television displays and coping with source content at different frame rates. Coping with high volumes of video data, in particular with high definition video content, puts high demands on the computer and so techniques that can minimise the overhead for video transmission are desired. Particular problems are faced with video capture for screencasting as a result of differences between the source video frame rate and capture frame rate. These differences can result in video judder owing to the mismatched frame rates.
Techniques that can maintain video quality in terms of resolution and frame rate are accordingly needed to ensure that the consumer's can experience high quality video footage of source content streaming from their computer.